diff --git a/Makefile b/Makefile
index f0949cb..9e99ea1 100644
--- a/Makefile
+++ b/Makefile
@@ -12,7 +12,8 @@
         test-e2e-deps test-e2e-api test-e2e-ui test-e2e-wg test-e2e \
         reset-test-admin-pass \
         show-admin-password reset-admin-password \
-        show-routes add-peer list-peers
+        show-routes add-peer list-peers \
+        ddns-update ddns-register
 
 # Detect docker compose command (v2 plugin preferred, fallback to v1 standalone)
 DC := $(shell docker compose version >/dev/null 2>&1 && echo "docker compose" || echo "docker-compose")
@@ -335,6 +336,21 @@ add-peer:
 		echo "Usage: make add-peer PEER_NAME=name PEER_IP=10.0.0.x PEER_KEY=<pubkey>"; \
 	fi
 
+# ── DDNS ─────────────────────────────────────────────────────────────────────
+
+ddns-update:
+	@python3 scripts/ddns_update.py
+
+ddns-register:
+	@DDNS_TOTP_SECRET="$(DDNS_TOTP_SECRET)" python3 -c "\
+import os, sys; sys.path.insert(0, 'scripts'); \
+from setup_cell import register_with_ddns, _read_existing_ip_range; \
+import json; \
+cfg = json.load(open('config/api/cell_config.json')) if os.path.exists('config/api/cell_config.json') else {}; \
+name = cfg.get('_identity', {}).get('cell_name', os.environ.get('CELL_NAME', 'mycell')); \
+import os; os.remove('data/api/.ddns_token') if os.path.exists('data/api/.ddns_token') else None; \
+register_with_ddns(name)"
+
 # ── Dev ───────────────────────────────────────────────────────────────────────
 
 dev:
diff --git a/scripts/ddns_update.py b/scripts/ddns_update.py
new file mode 100644
index 0000000..7d6d0d1
--- /dev/null
+++ b/scripts/ddns_update.py
@@ -0,0 +1,86 @@
+#!/usr/bin/env python3
+"""
+Update the cell's DDNS record with the current public IP.
+
+Called by: make ddns-update
+           systemd timer (optional, see scripts/pic-ddns-update.timer)
+
+Reads the DDNS token from data/api/.ddns_token (written by setup_cell.py).
+Exits 0 on success or if already up to date, non-zero on failure.
+"""
+import json
+import os
+import sys
+import urllib.error
+import urllib.request
+
+DDNS_URL = os.environ.get('DDNS_URL', 'https://ddns.pic.ngo/api/v1')
+ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+TOKEN_FILE = os.path.join(ROOT, 'data', 'api', '.ddns_token')
+IP_CACHE_FILE = os.path.join(ROOT, 'data', 'api', '.ddns_last_ip')
+
+
+def get_public_ip() -> str:
+    return urllib.request.urlopen('https://api.ipify.org', timeout=5).read().decode().strip()
+
+
+def read_token() -> str:
+    if not os.path.exists(TOKEN_FILE):
+        print('ERROR: DDNS token not found. Run "make setup" to register.', file=sys.stderr)
+        sys.exit(1)
+    return open(TOKEN_FILE).read().strip()
+
+
+def read_last_ip() -> str:
+    try:
+        return open(IP_CACHE_FILE).read().strip()
+    except FileNotFoundError:
+        return ''
+
+
+def write_last_ip(ip: str) -> None:
+    with open(IP_CACHE_FILE, 'w') as f:
+        f.write(ip)
+
+
+def main() -> int:
+    try:
+        public_ip = get_public_ip()
+    except Exception as e:
+        print(f'ERROR: Could not detect public IP: {e}', file=sys.stderr)
+        return 1
+
+    last_ip = read_last_ip()
+    if public_ip == last_ip:
+        print(f'DDNS: IP unchanged ({public_ip}) — no update needed')
+        return 0
+
+    token = read_token()
+    data = json.dumps({'token': token, 'ip': public_ip}).encode()
+    req = urllib.request.Request(
+        f'{DDNS_URL}/update',
+        data=data,
+        headers={'Content-Type': 'application/json'},
+        method='PUT',
+    )
+    try:
+        resp = urllib.request.urlopen(req, timeout=10)
+        result = json.loads(resp.read())
+        if result.get('updated'):
+            write_last_ip(public_ip)
+            print(f'DDNS: Updated to {public_ip}')
+            return 0
+        else:
+            print(f'ERROR: Unexpected response: {result}', file=sys.stderr)
+            return 1
+    except urllib.error.HTTPError as e:
+        body = e.read().decode()
+        print(f'ERROR: DDNS update failed ({e.code}): {body}', file=sys.stderr)
+        return 1
+    except Exception as e:
+        print(f'ERROR: DDNS update failed: {e}', file=sys.stderr)
+        return 1
+
+
+if __name__ == '__main__':
+    sys.exit(main())
diff --git a/scripts/setup_cell.py b/scripts/setup_cell.py
index 0c053ab..172185a 100644
--- a/scripts/setup_cell.py
+++ b/scripts/setup_cell.py
@@ -238,6 +238,74 @@ def ensure_session_secret():
     print('[CREATED] data/api/.session_secret')
 
 
+DDNS_URL = os.environ.get('DDNS_URL', 'https://ddns.pic.ngo/api/v1')
+DDNS_TOTP_SECRET = os.environ.get('DDNS_TOTP_SECRET', '')
+
+
+def register_with_ddns(cell_name: str) -> None:
+    """Register cell_name.pic.ngo with the DDNS server using TOTP auth.
+
+    Idempotent: if a token file already exists the registration is skipped.
+    Skipped silently if DDNS_TOTP_SECRET is not set.
+    """
+    token_path = os.path.join(ROOT, 'data', 'api', '.ddns_token')
+    if os.path.exists(token_path):
+        print('[EXISTS]  DDNS registration — token already present')
+        return
+
+    if not DDNS_TOTP_SECRET:
+        print('[SKIP]    DDNS_TOTP_SECRET not set — skipping DDNS registration')
+        return
+
+    import urllib.request
+    import urllib.error
+
+    # Detect public IP
+    try:
+        public_ip = urllib.request.urlopen(
+            'https://api.ipify.org', timeout=5
+        ).read().decode().strip()
+    except Exception as e:
+        print(f'[WARN]    Could not detect public IP: {e} — skipping DDNS registration')
+        return
+
+    # Generate TOTP code (requires pyotp; if not available fall back gracefully)
+    try:
+        import pyotp
+        otp = pyotp.TOTP(DDNS_TOTP_SECRET).now()
+    except ImportError:
+        # Try python3 -c as a subprocess fallback
+        try:
+            otp = subprocess.check_output(
+                ['python3', '-c', f"import pyotp; print(pyotp.TOTP('{DDNS_TOTP_SECRET}').now())"]
+            ).decode().strip()
+        except Exception as e:
+            print(f'[WARN]    pyotp not available and fallback failed: {e} — skipping DDNS')
+            return
+
+    data = json.dumps({'name': cell_name, 'ip': public_ip}).encode()
+    req = urllib.request.Request(
+        f'{DDNS_URL}/register',
+        data=data,
+        headers={'Content-Type': 'application/json', 'X-Register-OTP': otp},
+        method='POST',
+    )
+    try:
+        resp = urllib.request.urlopen(req, timeout=10)
+        result = json.loads(resp.read())
+        token = result['token']
+        os.makedirs(os.path.dirname(token_path), exist_ok=True)
+        with open(token_path, 'w') as f:
+            f.write(token)
+        os.chmod(token_path, 0o600)
+        print(f'[CREATED] DDNS registration: {result["subdomain"]}  ip={public_ip}')
+    except urllib.error.HTTPError as e:
+        body = e.read().decode()
+        print(f'[WARN]    DDNS registration failed ({e.code}): {body}')
+    except Exception as e:
+        print(f'[WARN]    DDNS registration failed: {e}')
+
+
 def bootstrap_admin_password():
     import secrets as _secrets
     users_file = os.path.join(ROOT, 'data', 'api', 'auth_users.json')
@@ -303,6 +371,7 @@ def main():
     write_caddy_config(ip_range, cell_name, domain)
     ensure_session_secret()
     bootstrap_admin_password()
+    register_with_ddns(cell_name)
 
     print()
     print('--- Setup complete! Run: make start ---')